Notes

What is Underpinning?

What is Underpinning?
<br>Underpinning a house, a residential dwelling or even a commercial building is the construction process of strengthening the foundation by building additional concrete or steel footings to stabilise or strengthen or lift the existing footings.
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<br>Underpinning is a construction process that adds extra footings beside and under your house so that your house is supported on soil that is more stable than the soils your home currently sits on.
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<br>The purpose of underpinning is to support your footings on soil that is more stable, stiffer, stronger and less likely to move in the future.
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<br>Google says, “Underpinning is a solid foundation laid below ground level to support or strengthen a building.”
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<br>When structural engineers specify underpinning in houses it is normally to support a house that is suffering from one downward reflection of soil and needs to be supported on deeper footings.
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<br>When Does a House need Underpinning?
<br>Underpinning is such a popular term right now in relation to fixing movement problems with houses. But is underpinning the right solution to your house movement problem?
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<br>House footings move for different reasons and not all footing movement requires underpinning.
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<br>So when is underpinning needed?
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<br>Underpinning is useful when the footings for a house or set of units have subsided or dropped for a reason that is unlikely to reverse.
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<br>Examples of footing movement that is unlikely to reverse are when a footing is constructed on loose or soft soil (such as uncontrolled fill).
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<br>If your house footings weren’t originally installed deep enough then underpin footings can be used to improve the stability of your house. They can even be used to jack your house back up to almost level.
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<br>When Is Underpinning Click Here For Additional Info Recommended?
<br>Footing movement that might reverse is caused by uneven changes in soil moisture content in clayey soils (also known as slab heave). Underpinning is not recommended for solving slab heave.
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<br>This movement is due to an effect that can be reversed. In our opinion, underpinning IS NOT the best way to solve issues with reactive clay movement.
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<br>How Is Concrete Underpinning Performed?
<br>Concrete underpinning a house normally involves digging new bored pier footings beside a house at 2m to 3m centres around the outside of the house.
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<br>Sometimes concrete underpins are also required inside the house. The underpin footings have to go deep enough to found into the soil that is strong enough to support the weight of the building.
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<br>Next, the deeper footings have to be joined to the existing building. Often this is achieved by digging under the existing footing (undermining the footing) to create a strong prop for the existing footing.
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<br>Then each pier and prop arrangement is reinforced with steel reinforcement bars and filled with concrete.
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<br>Clever underpinning contractors leave enough space between the underpin and the existing footing so that once the concrete is strong enough, the underpin can be used to jack the house up and make it level again.
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<br>Sometimes the jacking procedure will close up the settlement cracks that were in a house, but because the cracks sometimes dislodge unevenly the cracks won’t close up every time.
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<br>Is Underpinning Only Done on Outside Footings?
<br>No. The footings in the middle of a house can be underpinned too. The underpinning contractor has to dig through the slab to access the ground under the house, but then the underpinning work can continue as if the footing was on the outside of the house.
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<br>How Long Does Underpinning Take?
<br>How long the underpinning process takes depends on the number of underpins specified by the engineer.
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<br>Fur a house needing up to 10 underpins the work will be done over approximately two weeks.
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<br>If your whole house needs underpinning, then you might be out of your house for about a month.
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<br>In this article, we have touched on a few of the basics of underpinning. If you want more information, get in touch with your local underpinning contractor.
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My Website: https://adelaideunderpinning.com/